The present invention relates to a process for producing 2-alkylbenzanilide which is useful as agricultural germicide.
More particularly, it relates to an improved industrial process for producing 2-alkylbenzanilide having high purity by reacting an alkyl 2-alkylbenzoate with aniline or an aniline derivative.
The 2-alkylbenzanilides have high-germicidal effect and broad antimicrobial spectrum and are effective in preventing diseases, such as rice sheath blight, bacterial leaf blight, tomato late blight, cucumber anthracnose, haricot stem rot, alternaria leaf spot, powdery apple mildew, orange phoma rot, wheat bund, rusting of wheat, barley, turf, coffee, ornamental plants, vegetables, cereals and grasses, smut and Rhizoctonia and Fusarium soil diseases; and are also effective as disinfectants for seeds. It has been known to produce benzanilides having no substituent on benzene nucleus of benzoyl group by reacting an alkyl benzoate having no substituent on benzene nucleus with an aniline in the presence of an alcoholate e.g. sodium methylate in an organic solvent of a by-product of alcohol in an azeotropic condition.
For example, in Richard J. De Foo et al., Journal of Organic Chemistry Vol. 28, P 2915 (1963) and U.S. Pat. No. 3,462,486, benzanilides are produced by reacting ethyl benzoate with an aniline in benzene and a by-product of ethyl alcohol in an azeotropic condition in the presence of solid sodium methylate as shown in the following equation. ##STR3##
In order to smoothly proceed a condensation reaction of an alkyl carboxylate with an aniline, it is necessary to easily remove a by-product of alcohol out of a reaction system. Accordingly, it has been considered that the optimum condition is to use an organic solvent which is azeotropically distilled with the by-product of alcohol.
Benzene has been used as the organic solvent.
However, it has been hard to produce 2-alkyl benzanilides having high germicidal effect and broad antimicrobial spectrum in high yield by the conventional processes. That is, it has been hard to produce 2-alkylbenzanilide in high yield by reacting alkyl 2-alkyl benzoates which have a substituent at orth position to alkoxy carbonyl group with an aniline. In said processes, N-alkyl benzanilides have been easily produced as by-product, and it has been hard to completely inhibit the formation of the by-product.
When 2-alkylbenzanilide is contained with the by-product, the germicidal effect of 2-alkylbenzanilide may be adversely affected.
The inventors have studied to improve the conventional processes to inhibit the formation of the by-product of N-alkylbenzanilide so as to produce 2-alkylbenzanilides which have high germicidal effect and broad antimicrobial spectrum in high yield.
As the results, the inventors have found that the optimum condition is to react an alkyl 2-alkylbenzoate with an aniline in an organic solvent which is hardly azeotropically distilled with the by-product of alcohol.
The inventors have also found that the reactivity is different depending upon carbon atoms of the alkyl group of alkoxy carbonyl group of the alkyl 2-alkylbenzoate.
As the result of further studies, the inventors have found that 2-alkylbenzanilides can be produced in high yield without the formation of the by-product of N-alkylbenzanilide by reacting an alkyl 2-alkylbenzoate having the alkoxy carbonyl group having specific carbon atoms with an aniline in the presence of specific alcoholate in an organic solvent which is hardly azeotropically distilled with the by-product of alcohol.